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Open Source and information security mailing list archives
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Date: Thu, 11 Jan 2007 13:45:21 +0100 From: Erik Mouw <erik@...ddisk-recovery.com> To: Linus Torvalds <torvalds@...l.org> Cc: Aubrey <aubreylee@...il.com>, Hua Zhong <hzhong@...il.com>, Hugh Dickins <hugh@...itas.com>, linux-kernel@...r.kernel.org, hch@...radead.org, kenneth.w.chen@...el.com, akpm@...l.org, mjt@....msk.ru Subject: Re: O_DIRECT question On Wed, Jan 10, 2007 at 07:05:30PM -0800, Linus Torvalds wrote: > I should have fought back harder. There really is no valid reason for EVER > using O_DIRECT. You need a buffer whatever IO you do, and it might as well > be the page cache. There are better ways to control the page cache than > play games and think that a page cache isn't necessary. There is a valid reason: you really don't want to go through the page cache when a hard drive has bad blocks. The only way to get fast recovery and correct error reporting to userspace is by using O_DIRECT. > So don't use O_DIRECT. Use things like madvise() and posix_fadvise() > instead. Both don't do what I want it to do: only read the sector I request you to read and certainly do not try to outsmart me by doing some kind of readahead. Erik -- +-- Erik Mouw -- www.harddisk-recovery.com -- +31 70 370 12 90 -- | Lab address: Delftechpark 26, 2628 XH, Delft, The Netherlands - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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